Algae Scrubber Basics

[JohnnyB in SD]

A non-vertical screen only has flow on one side, so at best it is half as strong.

Half as strong as a vertical lit on two sides? I'll agree with that all day long.
But a screen lit on one side is already halved from two sided, so why halve a horizontal again from that? Halving twice means it would take 4 square feet to equal the 12" x 12". I would think that a 12" x 24" angled is comparable to a 12" x 12" vertical lit both sides because the illuminated surface area is equal? It appears to me that the effectiveness of angled/horizontal units is being highly discounted.
Don't get me wrong, I've been using verticals for the last couple/few years and they are the best thing I've ever done to maintain water quality. And for most (especially first time) users, they should be highly promoted over other configurations. But it seems the only reference to horizontals is how problematic and ineffective they are so don't even bother - end of story. There's little discussion regarding the challenges or how to overcome them.
I am maxed out space wise with 234 square inches of two sided verticals, which are difficult to access, causing me to neglect regular cleaning when I'm busy or lazy. I have the opportunity to use 576 Sq In of "horizontal" in the same or less space, which will be so easy to maintain I can make my 12 year old do it - and he will enjoy it.
I don't think it will take 936 Sq Inches to replace the verticals in filtering capacity if the flow and lighting is of equal strength.
I'm just trying to make an informed decision, and build if warranted without excessive trial and error.

 

[Floyd R Turbo]

Because horizontal is that much less efficient on an area basis - thing like islanding, shading, etc start to take effect. Plus horizontal will have depth to the water and this makes a huge impact on the boundary layer effect.

If you surge or pulse horizontal, this might circumvent this problem. But a plain horizontal raceway will perform poorly, so you need more area

Per my recent post though, I do now feel that a slanted screen, while one-sided, does not necessarily need to be considered horizontal unless the slant angle is very low (nearly horizontal)

 

[Brummie]

Half as strong as a vertical lit on two sides? I'll agree with that all day long.
But a screen lit on one side is already halved from two sided, so why halve a horizontal again from that? Halving twice means it would take 4 square feet to equal the 12" x 12". I would think that a 12" x 24" angled is comparable to a 12" x 12" vertical lit both sides because the illuminated surface area is equal? It appears to me that the effectiveness of angled/horizontal units is being highly discounted.
Don't get me wrong, I've been using verticals for the last couple/few years and they are the best thing I've ever done to maintain water quality. And for most (especially first time) users, they should be highly promoted over other configurations. But it seems the only reference to horizontals is how problematic and ineffective they are so don't even bother - end of story. There's little discussion regarding the challenges or how to overcome them.
I am maxed out space wise with 234 square inches of two sided verticals, which are difficult to access, causing me to neglect regular cleaning when I'm busy or lazy. I have the opportunity to use 576 Sq In of "horizontal" in the same or less space, which will be so easy to maintain I can make my 12 year old do it - and he will enjoy it.
I don't think it will take 936 Sq Inches to replace the verticals in filtering capacity if the flow and lighting is of equal strength.
I'm just trying to make an informed decision, and build if warranted without excessive trial and error.

If you google "Garfs B.a.d.a.s.s." you should be able to find my excessive trial and error. Mine works a treat.

 

[JohnnyB in SD]

Thank you very much for pointing me in that direction. Looks like it will take me some time to absorb and understand it all.

 

[JohnnyB in SD]

If you google "Garfs B.a.d.a.s.s." you should be able to find my excessive trial and error. Mine works a treat.

So if I'm understanding it correctly, you started with a small surge style growing chamber, then built a larger one with relatively consistent water level but incorporated a powerhead to create wavelike action similar to the pond barrel?
The last reports I've found end about 6 months ago. What are your latest observations, opinions, recommendations about them, especially pros/cons between the two?

 

[dre7606]

Thanks for the heatsink recommendation johnnyB!

 

[cubfanmatt]

Help please. My 5 month old waterfall scrubber is producing brown slime algae over the majority of my screen with the exceptions of some nice pockets of dark green hair algae. My nitrates are at 5 but I have to do 20% water changes every other week to keep it their.

I run GFO and skim 24/7
Screen is 5x10
Feed 2 cubes plus coral food
I have my screen lit on both sides using 660nm led from ebay
I have some hair algae in the display
Oh I have never rinsed my screen with fresh tap water...I didn't think it mattered but I guess I need to kill the pods on the screen?

Thanks I appreciate any help you can provide.

 

[Floyd R Turbo]

possibly need to rinse in FW. I would say once a month at a minimum, but it depends on the screen - how mature it is, how much growth, how rough it is initially, etc.

So N is 5, what is P?

5x10 = 50 sq in, lit on both sides would be 4 cubes/day but feeding 2, should be fine.

A picture would clarify this. Please post a pic of the screen under white light while water is running over it, if possible, or before cleaning if not.

Post a pic of the LED fixture, one with it on the scrubber in normal operation, one of the fixture itself turned off.

I suspect there is a possibility of photosaturation and thus you are getting only diatom growth in front of the LEDs. Please post specs on the LEDs and info on your photoperiod (how many hours/day, single vs split photoperiod throughout day, etc)

 

[cubfanmatt]

Thanks for your response Floyd.


My scrubber has been running for 5 months and I feel I have the screen roughed up. I only have a handful of holes not filled in with algae. My phosphates show 0 but my sand shows some brown so I think I must have some. The pics show 4 days worth of growth.

My lights I got from ebay. They are 20W Blue 554nm Red 660nm Hydroponic Plan Flood LED Grow Lights straight from China. These are the lights Daytek uses in the DIY Algae Turf Scrubber thread. Link below to the lights on ebay.

Thanks for your time!
Matt


http://www.ebay.com/itm/NEW-10W-20W...02?pt=US_Hydroponics&var=&hash=item35c5b3090e

 

[crn005]

So, let me ask y'all this. I have been playing with a design for about a month now to see what results I can get. I've always been curious about incorporating the scrubber into the baffles of the sump. I like that idea that you can get very consistent flow without all the trial and error of cutting the pipe. I know this brings about other downsides, but I wanted to see how well this style can do. Also, I realize others have utilized baffles before as well but have only seen one or two successful examples so I wanted to test it for myself.

What I did was create an acrylic box to simulate a fake baffle in the sump. Here's the general idea.

Then, I cut off part of my previous hang-on-side ats to reuse the part that holds the LEDs.

Then, I dialed in my pump with a ball valve to get it to 42-45gph per linear inch of screen.

The screen is held on by standard magnets that aren't rusting at all, so that's good. They hardly affect the flow considering that I left small tabs on the screen to xtend out to the side to give the magnets something to grab on to. Oh, and don't mind the mesh bag. That's my GAC!

This is the growth after about 3-4 weeks. It's hard to see because I took the picture through the side of the sump.

The screen is 1.75" away from the 2 660nm leds that are ran at 300mA. I was running at 9 hours a day at first but the growth ended up being yellowish so I bumped it down to 7 hours. It's still yellowish. This is after the fact that I have started dosing 2 Fergon tablets per week over the course of the past two weeks. The flow is perfect across the screen (much better than I've ever gotten with a slot-pipe, but maybe did a poor job previously). I just increased the light exposure to 18 hours a day, based off of recommendations of the standards for an ats, but felt the need to up my flow. Do y'all think that was the right move?

P.S. Oh, and the screen was one that I had used on my previous ats. I had left the screen in the sump just to try and maintain some of the growth (I wasn't happy with the yellow growth I was getting before. It started green but got yellow pretty quickly) but it was almost bare by the time I reused it. Let me know if I left any information about my tank out.

 

[crn005]

And notice that the growth just below the sump water level, despite being quaint, is very green. I've ran multiple scrubbers over the past couple of years and this one is stumping me. I just can't figure out why it's not getting much green growth on the screen by this point. My DT is almost bare of algae, because the CUC does a great job but I still have some patches of cyano in the sand.

And here's a picture of it in action, just in case.

 

[Floyd R Turbo]

crn005, interesting conundrum there. honestly I'd be guessing at what is going on. If I had to take a stab at it, I would say yellow growth = too much light for the amount of nutrients, so up the flow or decrease the photoperiod. Or, split the photoperiod so you put 30-60 minutes in between each section. But you were already at 7 and this is not a brand new screen.

One possibility is that since your screen is single-sided and is flat against a piece of acrylic, you might not be getting very good flow to the base of the screen. I think one part of the screen-sizing rule that is assumed is that if you are running a vertical screen, it is in a slot pipe - so you would be getting a sheet of water that trickles down the screen on both sides, no matter what, and the screen members cause the water to bounce around back and forth between the two sides somewhat. Without this, you end up with a lot of water bypassing the screen completely, even more so as you increase flow.

So my recommendation here is a simple one. Attach some 1/8" stand-off strips to the acrylic on the back side of the screen. They don't need to be long strips, even little squares would do it, spaced out maybe on 1" centers or something like that. Just enough to make the screen protrude out a bit and allow the water to flow through the material as it falls down.

I'm betting that will make a difference.

 

[Floyd R Turbo]

Thanks for your response Floyd.


My scrubber has been running for 5 months and I feel I have the screen roughed up. I only have a handful of holes not filled in with algae. My phosphates show 0 but my sand shows some brown so I think I must have some. The pics show 4 days worth of growth.

My lights I got from ebay. They are 20W Blue 554nm Red 660nm Hydroponic Plan Flood LED Grow Lights straight from China. These are the lights Daytek uses in the DIY Algae Turf Scrubber thread. Link below to the lights on ebay.

Thanks for your time!
Matt


http://www.ebay.com/itm/NEW-10W-20W...02?pt=US_Hydroponics&var=&hash=item35c5b3090e

This is the second build I've seen using these lights with nearly the exact same problem. Your screen has a lot more growth than the other one I saw though, that one was just had paper-thin growth but it was green around the edges and brown in the middle.

You are seeing photo-saturation resulting from the concentration of LEDs in the middle creating a hotspot on the screen. Add a diffuser in front of the fixtures. Lowe's, Plaskolite w/green & white label, in the ceiling tile section, $5 for a 24x48 sheet (find one with a crack and try to get a buck or two off). Cut with a utility knife while laying it bumpy side up on a piece of wood with another one on top (or a level, straightedge, etc) and make 3-4 passes and it will cut through. Don't 'score & snap' you'll end up with shards everywhere. Can also cut with dremel but kinda scary doing it that way.

Attach with velcro or zip ties so it doesn't fall off. That should help quite a bit. Please let me know if it does not!

 

[cubfanmatt]

Thanks Floyd and I appreciate the details you provide on the fix. I will let you know

 

[crn005]

crn005, interesting conundrum there. honestly I'd be guessing at what is going on. If I had to take a stab at it, I would say yellow growth = too much light for the amount of nutrients, so up the flow or decrease the photoperiod. Or, split the photoperiod so you put 30-60 minutes in between each section. But you were already at 7 and this is not a brand new screen.

One possibility is that since your screen is single-sided and is flat against a piece of acrylic, you might not be getting very good flow to the base of the screen. I think one part of the screen-sizing rule that is assumed is that if you are running a vertical screen, it is in a slot pipe - so you would be getting a sheet of water that trickles down the screen on both sides, no matter what, and the screen members cause the water to bounce around back and forth between the two sides somewhat. Without this, you end up with a lot of water bypassing the screen completely, even more so as you increase flow.

So my recommendation here is a simple one. Attach some 1/8" stand-off strips to the acrylic on the back side of the screen. They don't need to be long strips, even little squares would do it, spaced out maybe on 1" centers or something like that. Just enough to make the screen protrude out a bit and allow the water to flow through the material as it falls down.

I'm betting that will make a difference.

The top of the screen does have a lip that goes out from the wall it's on so some flow goes behind it, but probably not as much as what's on the front of it. I'll try taking it off of the wall a little bit. What do you think about bumping my exposure up to 18 hours though? I know the yellow growth means that it's either not getting enough nutrients or too much light. I'm thinking I might take the exposure back down to 7 hours per day to eliminate extra variables so I can find the culprit. If the flow doesn't fix it, then I can try the exposure time after that. Sound like a good idea? Also, about how long should I wait before I consider the modification a failure. Maybe a week? I would think it would show some type of improvement within that time frame if it was going to.

 

[Floyd R Turbo]

18 hours is the wrong direction unless you have a solid base of growth, and a jump from 7 to 18 is really bad, you should only increase the photoperiod by a few hours and then leave it for a week - don't make drastic changes, you need to find the 'sweet spot'. Too much high intensity light will cause photo saturation and the only thing that will grow will be diatoms.

 

[rog2961]

Are there any negatives to mounting the light outside the tank? Due to space issues, I can only tilt the lights down a bit to shine on the screen from above. If I mounted them outside the sump, they would shine through the glass, and the 1/4 acrylic box I made for it (only had the thick stuff lying around). The distance from the light to the screen would be about 7 inches or so. Using 23w cfl's with standard reflector. Dual lit, overflow fed. Was thinking of devising a way to do overflow fed and pump fed to increase flow.

I had one for a while before when I first started my tank and it worked well. I then got a skimmer and took the ats offline due to sound/space constraints. Tank was ok for a while, then algae started to take over. All sorts of different kinds, Tried lights out for 3 days and it helped but came back stronger. I seeded last night from my DT and have already seen growth with only a 10 hour photoperiod thus far. Hopefully this will help with the DT algae.

 

[Floyd R Turbo]

Besides extra distance and a little transmission loss, not really. Pic?

 

[rog2961]

Will need to get pics

 

[crn005]

You absolutely can get good growth through glass or acrylic. As a matter of fact, I've gotten good growth with light going through both to get to the screen. As Floyd said, you just have to compensate for it with a little extra intensity from your lights. Honestly though, by just using a visual comparison, you don't lose hardly any light going through the two. Just make sure you're maintaining the correct distance from the screen.